ORLANDO, Florida (AP) -- Trainers at Sea World's marine parks began wearing inflatable safety vests Monday whenever they work near killer whales, yet another safety measure implemented after the 2010 death of a trainer who was dragged into a pool by an orca.

The five-pound nylon vests can be inflated like an airplane life jacket and have a tube connecting to a small oxygen tank that fits in a pouch in the back, said Kelly Flaherty Clark, Sea World's curator of animal training. The vests took more than three years to develop with input from trainers, engineers and safety experts.

On Feb. 24, 2010, trainer Dawn Brancheau was interacting with Tilikum, a killer whale, in front of visitors in a pool at Shamu Stadium in Orlando when Tilikum grabbed her and pulled her off a platform into the pool, then refused to release her. Since Brancheau's death, trainers have been unable to get into the water with killer whales amid calls for new safety measures.

The 22 trainers who work at Shamu Stadium have been trained in the use of the vests, which could buy a trainer time to be rescued if the trainer fell into a pool.

"It's easy to use," Flaherty Clark said. "It's one of many changes that Sea World has made in the last four years."

Other changes include remotely controlled pool gates, new walkways around Shamu Stadium and an additional raised platform in an orca pool that could be used to lift a whale out of the water should a trainer fall in. But the vests are probably the most visible change that park visitors will notice, she said.

The start of using the vests had nothing to do with an appellate court's recent decision upholding a ruling that Sea World had violated a federal workplace safety law, Flaherty Clark added.

Earlier this month, that appellate court in Washington upheld a regulatory safety finding against Sea World by the Occupational Safety and Health Review Commission following an investigation into Brancheau's drowning. The court said Sea World had exposed trainers to recognized hazards when working in close contact with killer whales during performances.

Tilikum subsequently became the focus of the 2013 documentary film "Blackfish," which explores what may have caused Tilikum to kill Brancheau. The documentary argues that killer whales, when in captivity, become more aggressive to humans and each other. Since the documentary, several entertainers have pulled out of planned performances at SeaWorld Entertainment Inc. parks.

"The two things happened in completely different silos," Flaherty Clark said of the ruling and the use of the vests. "The team was close to complete before the ruling."